Circuits for generating electric impulses



Feb. 22, 1949. F. H. BRAY ET AL CIRCUITS FOR GENERATING ELECTRIC IMPULSES Filed NOVv 20, .1943

Patented Feb. 22, E949 CIRCUKTS FQR GENERATING ELECTRIC IMPULSES Frederick Harry Bray and Frank Ewart Newton,

London, England, assignors, by mesne assignments, to international Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application November 20, 1943, Serial No. 511,100 in Great Britain December 23, 1942 3 Claims. 1

This invention relates to a device for periodically opening and closing an electric circuit and has for its object to provide such a device in which the ratio between the lengths of the periods during which the circuit is open and closed respectively can be readily varied independently of the speed at which each closure (or opening) of the circuit recurs.

According to one feature of the present invention an arrangement for producing electric pulses by means of the operation and release of a relay are timed by a condenser and resistance circuit comprisingmeans for adjusting the speed of impulsing and independent means for adjusting the ratio of make and break in each or the impulses.

The nature or the invention will be clear from the following description of one embodiment thereof taken in conjunction with the accompanying drawing.

Referring to the drawing, the circuit is divided into two parts, one part, shown in the upper portion of the figure, for controlling the periodic action or rate of the impulses, and the other part, shown in the lower portion of the figure, for controlling the ratio of the open and closed periods of the output circuit. The impulsing portion of the circuit comprises the polarized rela P having two windings and 2 and one armature, and two relays PP and PR having four and two armatures respectively.

The input terminal 3, indicated as having a potential of 120 volts positive, is connected to the two windings l and 2 of the relay P through a resistance R8. and back contact pr! of the relay PR, a resistance R3 being included in the connection to winding 2. The other end of the winding 5 is connected through. a variable resistance R2 to ground at 4. The other end of the winding 2 is connected through the condenser Cl to ground at 4. The connections to these windings are arranged so that the fields produced will oppose each other when currents flow through the windings in parallel.

Across the condenser Cl is connected the front contact m2 of the relay PR in series with the back contact ppl of the relay PP and the resistance R9. A branch circuit including the resistance R1 is connected from the terminal 3 to a point between the variable resistance R2 and the winding l of the relay P.

Armature pi of the relay P is connected to ground and ti e front contact thereof is connected through the winding of the relay PP to a battery B. A timev constant circuit including the con" v to ground and its front contact is connected to a m ding of the relay PR, the other end of the :g be ng connected to the battery B. A time constant circuit comprising the condenser 04 and the resi tance R4 is connected between ground and the end of the winding of the PR relay other than that to which the battery is connected. The front contact pr! of the PR relay is nected to ground.

In the operation of the impulsing portion of the circui described above, current from the terminal 3 flows in several branches to ground at 4. One branch passes through resistor R8, back contact pr! of relay PR, winding I of relay P, resistor R2 to ground at 4. Current in another branch passes through resistance R8, back contact prl, resistance R3, winding 2 of relay P, condenser Ct, to ground at 4. Until the condenser Cl is charged to a predetermined amount current will thus flow through winding 2 of relay P in opposition to the current flowing through the winding i, and the relay P will remain for the time being in the position shown.

The various components are chosen so that the current flowing through winding 2 during this period when the condenser Cl is charging i greater than that flowing through the winding I. As the condenser charges however, this current will decay and eventually a time will be reached when the current flowing through the winding 2 is sufiiciently less than that flowing through winding I, to cause winding i to control the relay and cause its armature pl to assume its other position. It

will be seen that the adjustment of the variable resistance R2 will control the amount of current flowing through the winding I and will therefore control the time at which the current in winding i will be sufficient to cause the operation of the relay.

With the closure of front contact pl of the P relay, the circuit is closed through the PP relay,

but this relay does not operate immediately because of the condenser 03 and resistance R3 connected to it, since the condenser 03, having been previously charged, must discharge before the relay operates. Operation of the relay PP closes the circuit from ground through contact front, winding of relay PR, to battery at B. relay PR, however, is slow in operating because of the condenser C4 and resistor R4 connected between ground and its Winding.

The back contact pot of the relay PP maintains open the circuit across capacitance Cl which would otherwise be closed by the operation of front contact m2 of relay PR when that relay operates.

The operation of relay PR through its armature pri reverses the current flow through the P relay. The condenser Cl now acts as a battery, causing current to flow through the winding 2 of the relay P in the opposite direction, through resistance R3, front contact 1 11 of the relay PR, to ground at 'l, and from ground at 4 back to the condenser Cl. At the same time a circuit is closed fromv positive battery at terminal 3, through resistor Rl, winding l of relay P, front contact prl of relay PR, to ground at 1.

Again the components have been arranged such that the current from condenser Cl through the winding 2 is greater than that through the winding 1, and the relay P is held with its armature pl in the upper or'front position. During this time current is also flowing, as before, from terminal 3 through resistor R! and variable resistance R2 to ground at 4. The current flowing through winding 2 will decay as the condenser Cl discharges and when it has discharged enough, the current through winding I will be strong enough to operate the armature pl and cause it to assume the position shown in the drawing. Again it will be seen that the value of R2 will control the amount of current flowing through winding I and will thus determine the time at which the relay P will again operate.

Operation of the armature pl to the position shown in the drawing will break the circuit through the relay PP, but this relay will not release immediately, since current will flow from battery B through the winding of the relay into the condenser C3, and the relay Will not release until the condenser is charged sufliciently to 1'e duce the current flow below that at which the relay operates. The release of the relay PP will close the back contact ppl, and, since the front contact 101-2 of the PR relay is closed, a circuit will be closed from one side of condenser Cl through the front contact prZ of relay PR, back contact ppl of relay PP, resistance R9, to the other side of the condenser Cl, thus discharging the condenser as rapidly as the value of the resistance R9 will permit. The condenser Cl is thus discharged during the time between the release of the relay PP and the release of the relay PR.

When the relay PP releases and breaks the operating circuit for the relay PR, this relay does not immediately release because current will flow through the Winding thereof into the condenser C4, and the relay will not release until this ourrent-has decayed sufiiciently by the charging of the condenser.

- Therelease of the relay PR again connects the positive'terminal 3 to the left ends of the windings l, and 2 of relay P through the back of contact pr! and the cycle starts all over again.

The operation of the circuit controlling the make and break for the output which is shown in the lower portion of the figure comprises the rel'a'yRR and the gas tube T, which may be a cold cathode tube. V A- terminal 8 connected to the positive potential of 120 volts is connected through a resistance R50 to one end of the Winding of the RR relay and the other end of the winding is connected tothe armature ppZ of the relay PP. The make contact of the relay PPZ is connected to the anode of the gas tube T, the cathode of whichis connected to ground at 9.

The armature rrl of the relay RR is connected in the output circuit in order to close it when the relay operates and open it when the relay releases. v

The terminal 8 is also connected through the variable resistance R5 to the front terminal of the armature ppt of the relay PP, this armature being connected through the resitsance R6 to the control electrode of the tube T and through a condenser C2 to ground. The back contact of the armature ppd is connected through resistor R! to ground and forms a means of shorting and discharging the condenser CZ when the armature pp l is against the back contact.

The speed of impulsing and the ratio between the period during which contacts pl are in the position shown and the period during which they are in the other position may be varied by Varying resistances Rl, R2 and R3 and the capacity of condenser Cl, but each adjustment afiects both the speed and the ratio. In order therefore to have independent control of these two factors, we provide a separate means for varying the ratio of make-to-break in the impulses produced, and vary the speed of impulsing by varying resistance R2 only.

The adjustment for the make and break periods is provided by means of the condenser C2. When contacts pl change over, relay PP operates, as described above, and contacts @102 connect positive potential over relay RR to the anode of tube T, whilst contacts pp l connect condenser C2 into a charging circuit over the variable resistance R5. The condenser C2 commences to charge and when the potential applied through resistance R6 to the control electrode of tube T has risen sufliciently, a discharge is struck in the tube, relay RR operates and at its contacts rrl effects the desired closure of the controlled circuit. Relay RR continues operated until the contacts pl of relay P change over, whereupon the circuit of relay PP is broken, contacts pp open, relay RR is released and contacts rrl are opened. At the same time contacts change over and condenser C2 is discharged.

It will be clear that the interval between the closure of contacts pl' and the closure of contacts rrl is adjustable by adjusting the value of variable resistance R5 which regulates the rate of charge of condenser C2 and this adjustment is independent of any adjustment of the rate of operation of relay P. Thus by variation of resistance RZ-the number of impulses per second may be varied and by adjustment of R5 the ratio between the make and break periods of each impulse may be independently varied. With values for BI, R3 and Cl of 40,000 ohms, 8,000 ohms and 4 to 8 mi. respectively, the speed of impulsing may be varied from 1 per second to 3 per second by varying the value of resistance R2 from 5,000 ohms to zero. Independently of this, with a value of C2 of. 2 mi. the time elapsing between operation of contacts pl and operation of contacts rrl may be varied between 0 second and 990 milliseconds, by varying resistance R5 from zero to 250,000 ohms.

It will be appreciated that, although the latter adjustment is independent of the former, the make or break period of contacts rrl must not be made greater than the period between successive closures of contacts pl. It will also be appreciated that variation of resistance R2 affects the ratio between make and break periods in the impulses,

so that if a given ratio of make to break is to be.

preserved, R5 must be readjusted after R2 has been altered.

What is claimed is:

1. A device for periodically opening and closing an external electric circuit comprising a relay, means for causing the periodic movement of an armature of said relay from one of its positions to the other and back to the first position again, adjustable means for controlling the time at which said relay remains in each position, a coldcathode gas discharge tube having a control electrode, a, condenser, means for causing said condenser to charge when the armature of said relay moves to one of its positions, means connecting said condenser with said control electrode whereby the tube will discharge when the charge on said condenser reaches a predetermined amount, adjustable means for controlling the rate of charge of said condenser, switching means connected to said tube and controlled thereby for opening and closing the external circuit, and means for stopping the discharge of said tube when the armature of said relay moves to its other position.

2. A device for periodically opening and closing an external electric circuit according to claim 1, in which said means for causing periodic movement comprises a polarized relay having two magnetizing coils wound to produce magnetic fields opposing each other when currents flow through them in parallel, said adjustable means comprises a circuit for cyclically feeding currents in parallel through said two coils first in one direction and then in the other and for doing so over a con denser for both directions in the case of one of the coils, a source of electrical energy having one of its terminals connected to one end of the magnetizing winding of said first-mentioned relay,

the polarized relay having contacts for periodically connecting and disconnecting the other end of said Winding to the other terminal of said source, and a second condenser and a resistor connected in series between said other end of the magnetizing winding and said other terminal of the source for delaying the operation and release of said first-mentioned relay when its winding is respectively connected to and disconnected from said other terminal of the source.

3. A device for periodically opening and closing an external electric circuit comprising a charges, means for regulating the current in said two windings so that said relay will be held in one of its two operating positions for a predetermined time depending on the rate of decay of the charging current for said condenser and will then change to the other position, means controlled by the operation of said relay for connecting said condenser directly across the associated Winding of said relay, whereby said condenser will discharge through said winding, causing current to flow therethrough in the reverse direction, and for causing current to flow through the other winding of said relay in the reverse direction under control of said regulating means, whereby said relay will remain in its last-mentioned position until said condenser has discharged an amount determined by said regulating means and then change back to its first position, a gas discharge tube having a control electrode, asecond condenser, circuit means for causing said means controlled by the operation of said relay to initiate the charging of said second condenser, means connecting said condenser with said control electrode to cause said gas tube to discharge when the charge in said condenser has reached a predetermined value, means for causing the discharge of said tube to close the external electric circuit, means, under control of said relay, for cutting off the discharge in said tube, and control means for regulating the rate of charge of said second condenser.

FREDERICK HARRY BRAY. FRANK EWART NEWTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

